The term "electronic clutch" normally means a device able to automatically halt the power supply to the tool drive motor whenever the torque applied to the motor armature shaft exceeds a predetermined maximum value.
Currently used electronic clutches are based on electronic devices, known as klixons, which operate when the current absorbed by the tool exceeds a certain operating threshold (klixon opening current). This operation threshold can vary by as much as 20%, and depends on the tolerances of the devices used.
There is a tendency to provide electric tools, and in particular drilling machines, with two or more operating speeds, for which there should correspond two operating levels of the electronic clutch. An electronic clutch with two or more operating levels, if based on current klixon devices, would however require the use of a number of such devices, and a corresponding number of selection switches equal to the number of operating levels, resulting in a high tool cost.